In virtio_queue_host_notifier_aio_poll, not all "!virtio_queue_empty()" cases are making true progress. Currently the offending one is virtio-scsi event queue, whose handler does nothing if no event is pending. As a result aio_poll() will spin on the "non-empty" VQ and take 100% host CPU. Fix this by reporting actual progress from virtio queue aio handlers. Reported-by: Ed Swierk <eswierk@skyportsystems.com> Signed-off-by: Fam Zheng <famz@redhat.com> Tested-by: Ed Swierk <eswierk@skyportsystems.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
276 lines
7.7 KiB
C
276 lines
7.7 KiB
C
/*
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* Dedicated thread for virtio-blk I/O processing
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*
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* Copyright 2012 IBM, Corp.
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* Copyright 2012 Red Hat, Inc. and/or its affiliates
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*
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* Authors:
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* Stefan Hajnoczi <stefanha@redhat.com>
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*
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* This work is licensed under the terms of the GNU GPL, version 2 or later.
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* See the COPYING file in the top-level directory.
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*
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*/
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#include "qemu/osdep.h"
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#include "qapi/error.h"
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#include "trace.h"
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#include "qemu/iov.h"
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#include "qemu/thread.h"
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#include "qemu/error-report.h"
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#include "hw/virtio/virtio-access.h"
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#include "sysemu/block-backend.h"
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#include "hw/virtio/virtio-blk.h"
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#include "virtio-blk.h"
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#include "block/aio.h"
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#include "hw/virtio/virtio-bus.h"
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#include "qom/object_interfaces.h"
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struct VirtIOBlockDataPlane {
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bool starting;
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bool stopping;
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VirtIOBlkConf *conf;
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VirtIODevice *vdev;
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QEMUBH *bh; /* bh for guest notification */
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unsigned long *batch_notify_vqs;
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/* Note that these EventNotifiers are assigned by value. This is
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* fine as long as you do not call event_notifier_cleanup on them
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* (because you don't own the file descriptor or handle; you just
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* use it).
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*/
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IOThread *iothread;
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AioContext *ctx;
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};
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/* Raise an interrupt to signal guest, if necessary */
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void virtio_blk_data_plane_notify(VirtIOBlockDataPlane *s, VirtQueue *vq)
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{
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set_bit(virtio_get_queue_index(vq), s->batch_notify_vqs);
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qemu_bh_schedule(s->bh);
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}
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static void notify_guest_bh(void *opaque)
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{
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VirtIOBlockDataPlane *s = opaque;
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unsigned nvqs = s->conf->num_queues;
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unsigned long bitmap[BITS_TO_LONGS(nvqs)];
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unsigned j;
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memcpy(bitmap, s->batch_notify_vqs, sizeof(bitmap));
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memset(s->batch_notify_vqs, 0, sizeof(bitmap));
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for (j = 0; j < nvqs; j += BITS_PER_LONG) {
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unsigned long bits = bitmap[j];
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while (bits != 0) {
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unsigned i = j + ctzl(bits);
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VirtQueue *vq = virtio_get_queue(s->vdev, i);
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virtio_notify_irqfd(s->vdev, vq);
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bits &= bits - 1; /* clear right-most bit */
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}
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}
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}
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/* Context: QEMU global mutex held */
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void virtio_blk_data_plane_create(VirtIODevice *vdev, VirtIOBlkConf *conf,
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VirtIOBlockDataPlane **dataplane,
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Error **errp)
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{
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VirtIOBlockDataPlane *s;
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BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(vdev)));
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VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
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*dataplane = NULL;
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if (conf->iothread) {
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if (!k->set_guest_notifiers || !k->ioeventfd_assign) {
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error_setg(errp,
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"device is incompatible with iothread "
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"(transport does not support notifiers)");
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return;
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}
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if (!virtio_device_ioeventfd_enabled(vdev)) {
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error_setg(errp, "ioeventfd is required for iothread");
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return;
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}
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/* If dataplane is (re-)enabled while the guest is running there could
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* be block jobs that can conflict.
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*/
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if (blk_op_is_blocked(conf->conf.blk, BLOCK_OP_TYPE_DATAPLANE, errp)) {
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error_prepend(errp, "cannot start virtio-blk dataplane: ");
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return;
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}
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}
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/* Don't try if transport does not support notifiers. */
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if (!virtio_device_ioeventfd_enabled(vdev)) {
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return;
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}
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s = g_new0(VirtIOBlockDataPlane, 1);
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s->vdev = vdev;
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s->conf = conf;
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if (conf->iothread) {
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s->iothread = conf->iothread;
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object_ref(OBJECT(s->iothread));
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s->ctx = iothread_get_aio_context(s->iothread);
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} else {
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s->ctx = qemu_get_aio_context();
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}
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s->bh = aio_bh_new(s->ctx, notify_guest_bh, s);
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s->batch_notify_vqs = bitmap_new(conf->num_queues);
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*dataplane = s;
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}
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/* Context: QEMU global mutex held */
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void virtio_blk_data_plane_destroy(VirtIOBlockDataPlane *s)
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{
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VirtIOBlock *vblk;
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if (!s) {
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return;
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}
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vblk = VIRTIO_BLK(s->vdev);
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assert(!vblk->dataplane_started);
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g_free(s->batch_notify_vqs);
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qemu_bh_delete(s->bh);
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if (s->iothread) {
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object_unref(OBJECT(s->iothread));
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}
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g_free(s);
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}
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static bool virtio_blk_data_plane_handle_output(VirtIODevice *vdev,
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VirtQueue *vq)
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{
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VirtIOBlock *s = (VirtIOBlock *)vdev;
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assert(s->dataplane);
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assert(s->dataplane_started);
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return virtio_blk_handle_vq(s, vq);
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}
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/* Context: QEMU global mutex held */
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int virtio_blk_data_plane_start(VirtIODevice *vdev)
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{
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VirtIOBlock *vblk = VIRTIO_BLK(vdev);
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VirtIOBlockDataPlane *s = vblk->dataplane;
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BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(vblk)));
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VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
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unsigned i;
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unsigned nvqs = s->conf->num_queues;
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int r;
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if (vblk->dataplane_started || s->starting) {
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return 0;
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}
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s->starting = true;
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/* Set up guest notifier (irq) */
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r = k->set_guest_notifiers(qbus->parent, nvqs, true);
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if (r != 0) {
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fprintf(stderr, "virtio-blk failed to set guest notifier (%d), "
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"ensure -enable-kvm is set\n", r);
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goto fail_guest_notifiers;
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}
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/* Set up virtqueue notify */
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for (i = 0; i < nvqs; i++) {
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r = virtio_bus_set_host_notifier(VIRTIO_BUS(qbus), i, true);
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if (r != 0) {
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fprintf(stderr, "virtio-blk failed to set host notifier (%d)\n", r);
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while (i--) {
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virtio_bus_set_host_notifier(VIRTIO_BUS(qbus), i, false);
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}
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goto fail_guest_notifiers;
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}
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}
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s->starting = false;
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vblk->dataplane_started = true;
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trace_virtio_blk_data_plane_start(s);
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blk_set_aio_context(s->conf->conf.blk, s->ctx);
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/* Kick right away to begin processing requests already in vring */
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for (i = 0; i < nvqs; i++) {
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VirtQueue *vq = virtio_get_queue(s->vdev, i);
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event_notifier_set(virtio_queue_get_host_notifier(vq));
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}
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/* Get this show started by hooking up our callbacks */
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aio_context_acquire(s->ctx);
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for (i = 0; i < nvqs; i++) {
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VirtQueue *vq = virtio_get_queue(s->vdev, i);
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virtio_queue_aio_set_host_notifier_handler(vq, s->ctx,
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virtio_blk_data_plane_handle_output);
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}
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aio_context_release(s->ctx);
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return 0;
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fail_guest_notifiers:
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vblk->dataplane_disabled = true;
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s->starting = false;
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vblk->dataplane_started = true;
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return -ENOSYS;
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}
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/* Context: QEMU global mutex held */
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void virtio_blk_data_plane_stop(VirtIODevice *vdev)
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{
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VirtIOBlock *vblk = VIRTIO_BLK(vdev);
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VirtIOBlockDataPlane *s = vblk->dataplane;
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BusState *qbus = qdev_get_parent_bus(DEVICE(vblk));
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VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
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unsigned i;
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unsigned nvqs = s->conf->num_queues;
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if (!vblk->dataplane_started || s->stopping) {
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return;
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}
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/* Better luck next time. */
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if (vblk->dataplane_disabled) {
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vblk->dataplane_disabled = false;
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vblk->dataplane_started = false;
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return;
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}
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s->stopping = true;
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trace_virtio_blk_data_plane_stop(s);
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aio_context_acquire(s->ctx);
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/* Stop notifications for new requests from guest */
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for (i = 0; i < nvqs; i++) {
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VirtQueue *vq = virtio_get_queue(s->vdev, i);
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virtio_queue_aio_set_host_notifier_handler(vq, s->ctx, NULL);
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}
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/* Drain and switch bs back to the QEMU main loop */
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blk_set_aio_context(s->conf->conf.blk, qemu_get_aio_context());
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aio_context_release(s->ctx);
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for (i = 0; i < nvqs; i++) {
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virtio_bus_set_host_notifier(VIRTIO_BUS(qbus), i, false);
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}
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/* Clean up guest notifier (irq) */
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k->set_guest_notifiers(qbus->parent, nvqs, false);
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vblk->dataplane_started = false;
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s->stopping = false;
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}
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